Have horrible inefficient, uneven heat transfer with glass electric stove. Thought cheap pans that are not flat when hot. Bought All clad d5 pan in stainless and made big difference. Stainless is difficult for me to use with limited use application so purchased All clad HA1 anodized non stick. They are flat but for some reason have horrible heat transfer. Been using them for about a year. The reason for this post is other day wanted a really good sear on piece of beef and dusted off a old cast iron pan from storage. Was told not to use cast iron on glass. This pan has the heat ring cast into bottom so not much of pan actually makes contact with glass but thought would give it a try. All articles iv read say CI does not transfer heat efficient but holds heat. Was shocked that this pan heated 4 times faster and hotter than my HA1 aluminum and twice that of my $150 D5 pan. Thinking of purchasing a new CI pan without heat ring on bottom and grinding bottom smooth so less likely to scratch glass top. Have any of you had similar experiences with glass to cook ware?